Joseph Priestley

The whole business of philosophy, diversified as it is, is but one; it being one and the same great scheme, that all philosophers, of all ages and nations, have been conducting, from the beginning of the world.

There are many little attentions and precautions necessary to be observed in the conducting of experiments, which cannot well be described in words, but which it is needless to describe, since practice will necessarily suggest them...

This proved a very suitable and happy connexion, my wife being a woman of an excellent understanding, much improved by reading, of great fortitude and strength of mind, and of a temper in the highest degree affectionate and generous...

[The doctrine of air] I was led into in consequence of inhabiting a house adjoining to a public brewery, where I at first amused myself with making experiments on the fixed air [carbon dioxide] which I found ready made in the process of fermentation. When I removed from that house I was under the necessity of making the fixed air for myself; and one experiment leading to another, as I have distinctly and faithfully noted in my various publications on the subject, I by degrees contrived a convenient apparatus for the purpose, but of the cheapest kind.

It is known to all persons who are conversant in experimental philosophy, that there are many little attentions and precautions necessary to be observed in the conducting of experiments, which cannot well be described in words, but which it is needless to describe, since practice will necessarily suggest them; though, like all other arts in which the hands and fingers are made use of, it is only much practice that can enable a person to go through complex experiments, of this or any kind, with ease and readiness.

Experiments and Observations of Different Kinds of Air (1775)

Having thought it right to leave behind me some account of my friends and benefactors, it is in a manner necessary that I also give some account of myself; and as the like has been done by many persons, and for reasons which posterity has approved, I make no further apology for following their example. If my writings in general have been useful to my contemporaries, I hope that this account of myself will not be without its use to those who may come after me, and especially in promoting virtue and piety, which, I hope I may say, it has been my care to practise myself, as it has been my business to inculcate them upon others.

Memoirs of the Rev. Dr. Joseph Priestly (1809). p. 1

I married a daughter of Mr. Isaac Wilkinson, an ironmaster, near Wrexham, in Wales, with whose family I had become acquainted, in consequence of having the youngest son, William, at my school at Nantwich. This proved a very suitable and happy connexion, my wife being a woman of an excellent understanding, much improved by reading, of great fortitude and strength of mind, and of a temper in the highest degree affectionate and generous; feeling strongly for others, and little for herself. Also, greatly excelling in every thing relating to household affairs, she entirely relieved me of all concern of that kind, which allowed me to give all my time to the prosecution of my studies, and the other duties of my station.

The History of Electricity is a field full of pleasing objects, according to all the genuine and universal principles of taste, deduced from a knowledge of human nature.

The History of Electricity is a field full of pleasing objects, according to all the genuine and universal principles of taste, deduced from a knowledge of human nature. Scenes like these, in which we see a gradual rise and progress in things, always exhibit a pleasing spectacle to the human mind. Nature, in all her delightful walks, abounds with such views, and they are in a more especial manner connected with every thing that relates to human life and happiness; things, in their own nature, the most interesting to us. Hence it is, that the power of association has annexed crowds of pleasing sensations to the contemplation of every object, in which this property is apparent.
This pleasure, likewise, bears a considerable resemblance to that of the sublime, which is one of the most exquisite of all those that affect the human imagination. For an object in which we see a perpetual progress and improvement is, as it were, continually rising in its magnitude; and moreover, when we see an actual increase, in a long period of time past, we cannot help forming an idea of an unlimited increase in futurity; which is a prospect really boundless, and sublime.

Preface

The history of philosophy enjoys, in some measure, the advantages both of civil and natural history, whereby it is relieved from what is most tedious and disgusting in both. Philosophy exhibits the powers of nature, discovered and directed by human art. It has, therefore, in some measure, the boundless variety with the amazing uniformity of the one, and likewise every thing that is pleasing and interesting in the other. And the idea of continual rise and improvement is conspicuous in the whole study, whether we be attentive to the part which nature, or that which men are acting in the great scene.It is here that we see the human understanding to its greatest advantage, grasping at the noblest objects, and increasing its own powers, by acquiring to itself the powers of nature, and directing them to the accomplishment of its own views; whereby the security, and happiness of mankind are daily improved. Human abilities are chiefly conspicuous in adapting means to ends, and in deducing one thing from another by the method of analogy; and where may we find instances of greater sagacity, than in philosophers diversifying the situations of things, in order to give them an opportunity of showing their mutual relations, affections, and influences; deducing one truth and one discovery from another, and applying them all to the useful purposes of human life.If the exertion of human abilities, which cannot but form a delightful spectacle for the human imagination, give us pleasure, we enjoy it here in a higher degree than while we are contemplating the schemes of warriors, and the stratagems of their bloody art.

Preface

Great conquerors, we read, have been both animated, and also, in a great measure, formed by reading the exploits of former conquerors. Why may not the same effect be expected from the history of philosophy to philosophers? May not even more be expected in this case? The wars of many of those conquerors, who received this advantage from history, had no proper connection with former wars: they were only analogous to them. Whereas the whole business of philosophy, diversified as it is, is but one; it being one and the same great scheme, that all philosophers, of all ages and nations, have been conducting, from the beginning of the world; so that the work being the same, the. labours of one are not only analogous to those of of another, but in an immediate manner subservient to them; and one philosopher succeeds another in the same field; as one Roman proconsul succeeded another in carrying on the same war, and pursuing the same conquests, in the same country. In this case, an intimate knowledge of what has been done before us cannot but greatly facilitate our future progress, if it be not absolutely necessary to it.

Preface

The History and Present State of Discoveries Relating to Vision, Light, and Colours (1772)[edit]

Contemporary with Vitellio and Peccam was... Roger Bacon, a man of almost universal genius, and who wrote on almost every branch of science. He frequently quotes Alhazen on the subject of optics, and seems to have carefully studied his writings, as well as those of other Arabians, which were the fountains of natural knowledge in those days, and which had been introduced into Europe by means of the Moors in Spain. Notwithstanding the pains this great man took with the subject of opticks, it does not appear that, with respect to theory, he made any considerable advance upon what Alhazen had done before him.

Period I To the Revival of Letters in Erope

Great as Bacon was, he was far from being free from the mistakes and prejudices of those who went before him. Even some of the most wild and absurd opinions of the antients have the sanction of his approbation and authority. He does not hesitate to assent to an opinion... that visual rays proceed from the eye; giving this reason for it, that every thing in nature is qualified to discharge its proper functions by its own powers, in the same manner as the sun, and other celestial bodies. He acknowledges, however, that the presence of light, as well as several other circumstances, is necessary to vision.

Period I To the Revival of Letters in Erope

In his Opus Majus he demonstrates, that if a transparent body, interposed between the eye and an object, be convex towards the eye, the object will appear magnified. This observation our author certainly had from Alhazen... this writer [Bacon] gives us figures, representing the progress of rays of light through his spherical segment, as well as endeavours to give reasons why objects are magnified... From the writings of Alhazen and these observations and experiments of Bacon together, it is not improbable that some monks gradually hit upon the construction of spectacles, to which Bacon's lesser segment, not withstanding his mistake concerning it, was a nearer approach than Alhazen's... Whoever they were that pursued the discoveries of Bacon, they probably observed, that a very small convex glass, when held at a greater distance from a book, would magnify the letters more than when it was placed close to them, in which position only Bacon seemed to have used it. In the next place, they might try whether two of these small segments of a sphere placed together, or a glass convex on both sides, would not magnify more than one of them. They would then find, that two of these glasses, one for each eye, would answer the purpose of reading better than one; and lastly they might find, that different degrees of convexity, suited different persons. It is certain that spectacles were well known in the 13th century, and not long before. ...It would certainly have been a great satisfaction to us to have been able to trace the actual steps in the progress of this most useful invention, without which most persons who have a taste for reading must have had the melancholy prospect of passing a very dull and joyless old age; and must have been deprived of the pleasure of entertaining themselves by conversing with the absent and the dead, when they were no longer capable of acting their part among the living. Telescopes and microscopes are to be numbered among the superfluities of life when compared to spectacles, which may now be ranked almost among the necessities of it; since the arts of reading and writing are almost universal.

The mind of man can never be wholly barren. Through our whole lives we are subject to successive impressions; for, either new ideas are continually flowing in, or traces of the old ones are marked deeper.

Religious rights, and religious liberty, are things of inestimable value.

As all finite things require a cause, infinites admit of none … we are constrained, in pursuing the train of causes and effects, to stop at last at something uncaused.

It is the earnest wish of my heart, that your minds may be well established in the sound principles of religious knowledge, because I am fully persuaded, that nothing else can be a sufficient foundation of a virtuous and truly respectable conduct in life, or of good hope in death. A mind destitute of knowledge (and, comparatively speaking, no kind of knowledge, besides that of religion, deserves the name) is like a field on which no culture has been bestowed, which, the richer it is, the ranker weeds it will produce, If nothing good be sown in it, it will be dccupied by plants that are useless or noxious.

Vol. I : The Dedication (March 1772)

The mind of man can never be wholly barren. Through our whole lives we are subject to successive impressions; for, either new ideas are continually flowing in, or traces of the old ones are marked deeper. If, therefore, you be not acquiring good principles be assured that you are acquiring bad ones; if you be not forming virtuous habits you are, how insensibly soever to yourselves, forming vicious ones…

Vol. I : The Dedication (March 1772)

Respect a parliamentary king, and chearfully pay all parliamentary taxes; but have nothing to do with a parliamentary religion, or a parliamentary God.Religious rights, and religious liberty, are things of inestimable value. For these have many of our ancestors suffered and died; and shall we, in the sunshine of prosperity, desert that glorious cause, from which no storms of adversity or persecution could make them swerve? Let us consider if as a duty of the first rank with respect to moral obligation, to transmit to our posterity, and provide, as far as we can, for transmitting, unimpaired, to the latest generations, that generous zeal for religion and liberty, which makes the memory of our forefathers so truly illustrious.

Vol. I : The Dedication (March 1772)

The mind of man will never be able to contemplate the being, perfections, and providence of God without meeting with inexplicable difficulties. We may find sufficient reason for acquiescing in the darkness which involves these great subjects, but we must never expect to see them set in a perfectly clear light. But notwithstanding this, we may know enough of the divine being, and of his moral government, to make us much better and happier beings than we could be without such knowledge; and even the consideration of the insuperable difficulties referred to above is not without its use, as it tends to impress the mind with sentiments of reverence, humility, and submission.

Vol. I : Preface (1772)

If any person, discouraged by these difficulties, should think to relieve himself by rejecting all religion, natural and revealed, he will find, if he reflect at all, that he has miserably deceived himself, and that he is involved in greater perplexity than ever; the scheme he has adopted not only filling his mind with great darkness and distress, but being contrary to some of the plainest appearances in nature, and therefore manifestly irrational and absurd.

Vol. I : Preface (1772)

When we say there is a GOD, we mean that there is an intelligent designing cause of what we see in the world around us, and a being who was himself uncaused.

Vol. I : Part I : The Being and Attributes of God, § 1 : Of the existence of God, and those attributes which art deduced from his being considered as uncaused himself, and the cause of every thing else (1772)

It may, perhaps, be true, though we cannot distinctly see it to be so, that as all finite things require a cause, infinites admit of none. It is evident, that nothing can begin to be without a cause; but it by no means follows from thence, that that must have had a cause which had no beginning. But whatever there may be in this conjecture, we are constrained, in pursuing the train of causes and effects, to stop at last at something uncaused.
That any being should be self created is evidently absurd, because that would suppose that he had a being before he had, or that he existed, and did not exist at the same time. For want of clearer knowledge of this subject, we are obliged to content ourselves with terms that convey only negative ideas, and to say that God is a being untreated or uncaused; and this is all that we mean when we sometimes say that he is self existent.

Vol. I : Part I : The Being and Attributes of God, § 1 : Of the existence of God, and those attributes which art deduced from his being considered as uncaused himself, and the cause of every thing else (1772)

The unity of God is a doctrine on which the greatest stress is laid in the whole system of revelation

The Jews were taught by their prophets to expect a Messiah…a person in whom themselves and all the nations of the earth should be blessed…

We, who only learn from history that crucifixion was a kind of death to which slaves and the vilest of malefactors were exposed, can but very imperfectly enter into their prejudices, so as to feel what they must have done with respect to it.

Most of the early Christian writers thought the text "I and my Father are one," was to be understood of an unity or harmony of disposition only.

The whole doctrine of atonement, with every modification of it, has been a departure from the primitive and genuine doctrine of Christianity.

The unity of God is a doctrine on which the greatest stress is laid in the whole system of revelation. To guard this most important article was the principal object of the Jewish religion; and, notwithstanding the proneness of the Jews to idolatry, at length it fully answered its purpose in reclaiming them, and in impressing the minds of many persons of other nations in favour of the same fundamental truth.
The Jews were taught by their prophets to expect a Messiah, who was to be descended from the tribe of Judah, and the family of David, — a person in whom themselves and all the nations of the earth should be blessed; but none of their prophets gave them an idea of any other than a man like themselves in that illustrious character, and no other did they ever expect, or do they expect to this day.JesusChrist, whose history answers to the description given of the Messiah by the prophets, made no other pretensions; referring all his extraordinary power to God, his Father, who, he expressly says, spake and acted by him, and who raised him from the dead: and it is most evident that the apostles, and all those who conversed with our Lord before and after his resurrection, considered him in no other light than simply as "a man approved of God, by wonders and signs which God did by him."

Part I : The History of Opinions Relating to Jesus Christ, Introduction

As the greatest things often take their rise from the smallest beginnings, so the worst things sometimes proceed from good intentions. This was certainly the case with respect to the origin of Christian Idolatry. All the early heresies arose from men who wished well to the gospel, and who meant to recommend it to the Heathens, and especially to philosophers among them, whose prejudices they found great difficulty in conquering. Now we learn from the writings of the apostles themselves, as well as from the testimony of later writers, that the circumstance at which mankind in general, and especially the more philosophical part of them, stumbled the most, was the doctrine of a crucified Saviour. They could not submit to become the disciples of a man who had been exposed upon a cross, like the vilest malefactor. Of this objection to Christianity we find traces in all the early writers, who wrote in defence of the gospel against the unbelievers of their age, to the time of Lactantius; and probably it may be found much later. He says, "I know that many fly from the truth out of their abhorrence of the cross." We, who only learn from history that crucifixion was a kind of death to which slaves and the vilest of malefactors were exposed, can but very imperfectly enter into their prejudices, so as to feel what they must have done with respect to it. … Though this circumstance was "unto the Jews a stumbling-block, and unto the Greeks foolishness," it was to others "the power of God and the wisdom of God." 1 Cor. i. 23, 24. For this circumstance at which they cavilled, was that in which the wisdom of God was most conspicuous; the death and resurrection of a man, in all respects like themselves, being better calculated to give other men an assurance of their own resurrection, than that of any super-angelic being, the laws of whose nature they might think to be very different from those of their own. But, "since by man came death, so by man came also the resurrection of the dead."
Later Christians, however, and especially those who were themselves attached to the principles of either the Oriental or the Greek philosophy, unhappily took another method of removing this obstacle; and instead of explaining the wisdom of the divine dispensations in the appointment of a man, a person in all respects like unto his brethren, for the redemption of men, and of his dying in the most public and indisputable manner, as a foundation for the clearest proof of a real resurrection, and also of a painful and ignominious death, as an example to his followers who might be exposed to the same … they began to raise the dignity of the person of Christ, that it might appear less disgraceful to be ranked amongst his disciples.

Part I : The History of Opinions Relating to Jesus Christ,

We find upon all occasions, the early Christian writers speak of the Father as superior to the Son, and in general they give him the title of God, as distinguished from the Son; and sometimes they expressly call him, exclusively of the Son, the only true God; a phraseology which does not at all accord with the idea of the perfect equality of all the persons in the Trinity. But it might well be expected, that the advances to the present doctrine of the Trinity should be gradual and slow. It was, indeed, some centuries before it was completely formed.

Part I : The History of Opinions Relating to Jesus Christ, § III : The Supremacy was always ascribed to the Father before the Council Of Nice

Most of the early Christian writers thought the text "I and my Father are one," was to be understood of an unity or harmony of disposition only. Thus Tertullian observes, that the expression is unum, one thing, not one person; and he explains it to mean unity, likeness, conjunction, and of the love that the Father bore to the Son. Origen says, "let him consider that text, 'all that believed were of one heart and of one soul,' and then he will understand this, 'I and my Father are one.'"

Part I : The History of Opinions Relating to Jesus Christ, § III : The Supremacy was always ascribed to the Father before the Council Of Nice

It is sufficiently evident from many circumstances, that the doctrine of the divinity of Christ did not establish itself without much opposition, especially from the unlearned among the Christians, who thought that it savoured of Polytheism, that it was introduced by those who had had a philosophical education, and was by degrees adopted by others, on account of its covering the great offence of the cross, by exalting the personal dignity of our Saviour.

Part I : The History of Opinions Relating to Jesus Christ, § IV : Of the Difficulty with which the Doctrine of the Divinity of Christ was Established.

As I conceive this doctrine to be a gross misrepresentation of the character and moral government of God, and to affect many other articles in the scheme of Christianity, greatly disfiguring and depraving it; I shall show, in a fuller manner than I mean to do with respect to any other corruption of Christianity, that it has no countenance whatever in reason, or the Scriptures; and, therefore, that the whole doctrine of atonement, with every modification of it, has been a departure from the primitive and genuine doctrine of Christianity.

On conventional doctrines of Jesus Christ's atonement for sins, in Part II : Opinions Relating to the Doctrine of Atonement, Introduction

It is hardly possible not to suspect the truth of this doctrine of atonement, when we consider that the general maxims to which it may be reduced, are nowhere laid down, or asserted, in the Scriptures, but others quite contrary to them.

Part II : Opinions Relating to the Doctrine of Atonement, § I : That Christ did not die to make satisfaction for the sins of men.

Whenever our Lord speaks of the object of his mission and death, as he often does, it is either in a more general way, as for the salvation of the world, to do the will of God, to fulfil the scripture prophecies … or more particularly, to give the fullest proof of his mission by his resurrection from the dead, and an assurance of a similar resurrection of all his followers. He also compares his being raised upon the cross to the elevation of the serpent in the wilderness, and to seed buried in the ground, as necessary to its future increase. But all these representations are quite foreign to anything in the doctrine of atonement.

Part II : Opinions Relating to the Doctrine of Atonement, § I : That Christ did not die to make satisfaction for the sins of men.

From the fame opinion of a soul distinct from the body came the practice of praying, first for the dead, and then to them with a long train of other absurd opinions, and superstitious practices.

General Conclusions, Part I Containing Considerations addressed to Unbelievers and especially to Mr. Gibbon

That miracles are things in themselves possible, must be allowed so long as it is evident that there is in nature a power equal to the working of them. And certainly the power, principle, or being, by whatever name it be denominated, which produced the universe, and established the laws of it, is fully equal to any occasional departures from them. The object and use of those miracles on which the christian religion is founded, is also maintained to be consonant to the object and use of the general system of nature, viz. the production of happiness. We have nothing, therefore to do, but to examine, by the known rules of estimating the value of testimony whether there be reason to think that such miracles have been wrought, or whether the evidence of Christianity, or of the christian history, does not stand upon as good ground as that of any other history whatever.

General Conclusions, Part I

Indeed, if any man can say, that it is not an interesting question, whether his existence terminate at death, or is to be resumed at a future period, and then to continue for ever, he must be of a low and abject mind. To a rational being, capable of contemplating the wonders of nature, and of investigating the laws of it, and to a being of a social disposition, his existence, and the continuance of his rational faculties, must be an object of unspeakable value to him; and consequently he must ardently wish that christianity... may be true. For to a philosopher, who forms his judgment by what he actually observes, the doctrine of soul, capable of subsisting and acting when the body is in the grave, will never give any satisfaction. To every person, therefore, who is capable of enjoying his existence, the christian doctrine of a resurrection opens a glorious and transporting prospect.

General Conclusions, Part I

I am sorry... to have occasion to admonish Mr. Gibbon, that he should have distinguished better than he has done between christianity itself, and the corruptions of it. ...He should not have taken it for granted, that the doctrine of three persons in one God, or the doctrine of atonement for the sins of all mankind, by the death of one man, were any parts of the christian system; when, if he had read the New Testament for himself, he must have seen the doctrine of the proper unity of God, and also that of his free mercy to the penitent, in almost every page of it.

General Conclusions, Part I

Too many christians have been chargeable with... confounding the Logos of Plato with that of John, and making of it a second person in the trinity, than which no two things can be more different.

General Conclusions, Part I

Mr. Gibbon has much to learn concerning the gospel before he can be properly qualified to write against it. Hitherto he seems to have been acquainted with nothing but the corrupt establishments of what is very improperly called Christianity; whereas it is incumbent upon him to read and study the New Testament for himself. There he will find nothing like Platonism, but doctrines in every respect the reverse of that system of philosophy, which weak and undistinguishing christians afterwards incorporated with it.

General Conclusions, Part I

Had Mr. Gibbon lived in France, Spain, or Italy, he might with the fame reason have ranked the doctrine of transubstantiation, and the worship of saints and angels among the essentials of Christianity, as the doctrines of the trinity and of the atonement.

General Conclusions, Part I

The friends of genuine, and I will add of rational Christianity, have not,... on the whole, much reason to regret that their enemies have not made these distinctions; since by this means, we have been taught to make them ourselves; so that Christianity is perhaps as much indebted to its enemies, as to its friends, for this important service. In their indiscriminate attacks, whatever has been found to be untenable has been gradually abandoned, and I hope the attack will be continued till nothing of the wretched outworks be left; and then, I doubt not, a safe and impregnable fortress, will be sound in the center, a fortress built upon a rock, against which the gates of death will not prevail.

General Conclusions, Part I Containing Considerations addressed to Unbelievers and especially to Mr. Gibbon

What does Priestley mean, by an unbeliever, when he applies it to you? How much did he unbelieve himself? Gibbon had it right when he denominated his Creed, "scanty." We are to understand, no doubt, that believed the resurrection of Jesus, some of his miracles, his inspiration; but in what degree? He did not believe in the inspiration of the writings that contain his history. Yet he believed in the Apocalyptic beast, and he believed as much as he pleased in the writings of Daniel and John. This great and extraordinary man, whom I sincerely loved, esteemed, and respected, was really a phenomenon; a comet in the system, like Voltaire, Bolingbroke, and Hume. Had Bolingbroke or Voltaire taken him in hand, what would they have made of him and his Creed?

That the vegetable creation should restore the air which is spoiled by the animal part of it, looks like a rational system, and seems to be of a piece with the rest. Thus fire purifies water all the world over. It purifies it by distillation, when it raises it in vapours, and lets it fall in rain; and farther still by filtration, when keeping it fluid, it suffers that rain to percolate the earth. We knew before that putrid animal substances were converted into sweet vegetables when mixed with the earth and applied as manure; and now, it seems, that the same putrid substances, mixed with the air, have a similar effect. The strong, thriving state of your mint, in putrid air, seems to show that the air is mended by taking something from it, and not by adding to it. I hope this will give some check to the rage of destroying trees that grow near houses, which has accompanied our late improvements in gardening, from an opinion of their being unwholesome. I am certain, from long observation, that there is nothing unhealthy in the air of woods; for we Americans have everywhere our country habitations in the midst of woods, and no people on earth enjoy better health or are more prolific.

Yours is one of the few lives precious to mankind, and for the continuance of which every thinking man is solicitous. Bigots may be an exception. What an effort, my dear sir, of bigotry in politics and religion have we gone through! The barbarians really flattered themselves they should be able to bring back the times of Vandalism, when ignorance put everything into the hands of power and priestcraft. All advances in science were proscribed as innovations. They pretended to praise and encourage education, but it was to be the education of our ancestors. We were to look backwards, not forwards, for improvement … This was the real ground of all the attacks on you. Those who live by mystery and charlntanerie, fearing you would render them useless by simplifying the Christian philosophy — the most sublime and benevolent, but most perverted system that ever shone on man — endeavored to crush your well-earned and well-deserved fame. But it was the Lilliputians upon Gulliver. Our countrymen have recovered from the alarm into which art & industry had thrown them; science & honesty are replaced on their high ground; and you, my dear Sir, as their great apostle, are on it's pinnacle.

Why were Priestley, Boyle and Black able to see the question clearly enough to begin trying to answer it? ...because they had new tools. The air pump designed by Otto von Guericke and Boyle (...in collaboration with his assistant Robert Hooke...) were essential to Priestley's lab in Leeds. ...In a way, the air pump had enabled the entire field of pneumatic chemistry in the seventeenth century.

The Royal Society... voted to award him the Copley Medal, the most prestigious scientific prize of its day, "on account of the many curious and useful Experiments contained in his observations on different kinds of Air." In receiving the prize, Priestley was joining the ranks of his friends Canton and Franklin, who had three medals between them. Only five years after they had encouraged him to turn his experimental hobbies into a serious vocation, Priestly had reached the highest pinnacle of scientific achievement.

In 1774 he thought he had obtained nitrous oxide... in 1775 he saw the gas as dephlogisticated air... If we refuse the palm to Priestley, we cannot award it to Lavoisier for the work of 1775... Lavoisier insisted that oxygen was an atomic "principle of acidity"… formed only when that "principle" united with "caloric"... Ignoring Scheele, we can safely say that oxygen had not been discovered before 1774, and we would probably say that it had been discovered by 1777 or shortly thereafter. But... any attempt to date the discovery must inevitably be arbitrary because discovering a new sort of phenomenon is necessarily a complex event, one which involves recognizing both that something is and what it is.

Few men have had to struggle for so many years with circumstances more straitened and precarious than my father...

Few men have had to struggle for so many years with circumstances more straitened and precarious than my father; few men have ventured to attack so many or such inveterate prejudices respecting the prevalent religion of his country, or have advanced bolder or more important opinions in opposition to the courtly politics of the powers that be; few have had to encounter more able opponents in his literary career, or have been exposed to such incessant and vindictive obloquy, from men of every description, in return for his unremitting exertions in the cause of truth; yet none have more uniformly proceeded with a single eye, regardless of consequences, to act as his conviction impelled him, and his conscience dictated. His conduct brought with it its own reward, reputation, and respect, from the most eminent of his contemporaries, the affectionate attachment of most valuable friends, and a cheerfulness of disposition arising in part from conscious rectitude which no misfortunes could long repress. But to me it seems, that conscious rectitude alone would hardly of itself have been able to support him under some of the afflictions he was doomed to bear.He had a farther resource, to him never failing and invaluable, a firm persuasion of the benevolence of the Almighty towards all his creatures, and the conviction that every part of his own life, like every part of the whole system, was preordained for the best upon the whole of existence. Had he entertained the gloomy notions of Calvinism, in which he was brought up, this cheering source of contentment and resignation would probably have failed him, and irritation and despondency would have gained an unhappy ascendancy. But by him the deity was not regarded as an avenging tyrant, punishing, for the sake of punishing his weak and imperfect creatures, but as a wise and kind parent, inflicting those corrections only that are necessary to bring our dispositions to the proper temper, and to fit us for the highest state of happiness of which our natures are ultimately capable.

His son, Joseph Priestley, in the Preface (1 May 1805) to Memoirs of the Rev. Dr. Joseph Priestly (1809), p. 41